Resonant and semi-resonant DC-DC voltage converters, including isolated and non-isolated topologies, are used in a variety of applications including telecommunications, consumer electronics, computer power supplies, etc. The usage of such converters is gaining popularity because of their zero-voltage and/or zero-current switching characteristics, and their ability to utilize parasitic electrical properties inherent in an electronic circuit. Such converters provide advantages including lower cost and higher efficiency as compared to other types of converters.
The output current of many resonant and semi-resonant voltage converters takes the shape of the upper half cycle of a sinusoid, wherein this shape occurs during each switching cycle of such voltage converters. These converters are often controlled using a variable switching frequency in order to meet their associated load requirements, which may vary over time. Multiple phases of such converters may be connected in parallel in order to increase the available load current and in order to reduce ripple at the output of such converters.
A high-performance voltage converter needs current information for each of its phases in order to provide high-quality power to its load. Such phase current information is critical in providing key features such as phase fault detection, peak current protection, phase balancing, accurate load line estimation, power saving modes, over-current protection, and improved transient response. Conventional switching power converters, including resonant converters, include current sensing/sampling networks for obtaining phase current information. However, conventional current sampling networks consume significant power and require a relatively large die area.
For example, one conventional approach for sampling phase current information makes use of flash analog-to-digital converters (ADCs). While such ADCs provide can provide fast conversion and high precision, they are relatively expensive, have high leakage current even when they are not actively converting, use high power while they are converting, and require significant die area on a controller chip or elsewhere within a voltage converter. Another conventional approach for obtaining phase current information makes use of tracking ADCs. However, tracking ADCs are susceptible to noise, require relatively high power, consume significant die area, and have poor tracking capability and performance at high currents.
Accordingly, there is a need for improved phase current estimation techniques that may be used by resonant or semi-resonant voltage converters, wherein the estimation techniques consume low power and die area, while providing accurate and fast phase current tracking.